Molluscan Research

Discovery of an established population of a non-native species of Viviparidae (Caenogastropoda) in Argentina

2023-07-31T15:21:51+12:00

Discovery of an established population of Sinotaia quadrata (Benson, 1842) in a river and reservoir in Argentina is reported, representing the first report of a Recent viviparid species in South America. Viviparids are a family of freshwater snails occurring nearly worldwide. A study of the shell and aspects of the anatomy of S. quadrata are presented. It is distinguished from other native taxa by its large shell size, presence of a blackish axial band on the columellar side of the aperture and two to three carina on the body whorl. The invasive species Physa acuta Draparnaud, 1805 (Physidae) and Corbicula fluminea (Müller, 1774) (Corbiculidae) also inhabit the same sites as Sinotaia quadrata. Co-occurring native species of molluscs are Pomacea canaliculata (Lamarck, 1822) (Ampullariidae) and Biomphalaria tenagophila (d´Orbigny, 1835) (Planorbidae). This record increases the total number of invasive gastropods in Argentina to six.

**Shell colouration and antioxidant defence capacity in Theba pisana (O.F. Müller, 1774)**

2023-07-31T15:27:31+12:00

Theba pisana (Müller, 1774), a Mediterranean snail, is known for its heat tolerance and its remarkable shell colour polymorphism ranging from pale white to darkly striped, although darker morphs are considered less vital in hot habitats due to presumably stronger absorption of radiation. Melanin, the black pigment of these snails, is known as an effective antioxidant, and elevated temperatures can increase oxidative stress. By analysing oxidative waste products via the ferrous oxidation xylenol orange (FOX) assay as a marker for the lipid peroxidation level, we aimed at investigating possible links between heat stress, colouration and antioxidant defence capacity in T. pisana. Although we found increasing levels of peroxidation products with increasing heat exposure duration, there was no difference in antioxidant defence capacity observable between different morphs of T. pisana. Hence the avoidance of lipid peroxidation as an environmentally relevant factor for the maintenance of melanistic morphs in strongly illuminated habitats can be considered improbable.

The Recent Typhinae (Gastropoda: Muricidae) of New Zealand

2023-07-31T15:33:53+12:00

The Recent Typhinae from the New Zealand region are reviewed. Four species are recognized: Monstrotyphis pauperis (Mestayer, 1916), M. montfortii (A. Adams, 1863), M. tangaroa n. sp. and Siphonochelus solus Vella, 1961. A possible fifth species, known from a single, subadult specimen, remains unidentified.

**A new species of Crepipatella (Gastropoda: Calyptraeidae) from northern Chile**

2023-07-31T15:37:49+12:00

Crepipatella occulta n. sp. is described from the intertidal zone in northern Chile. This species is morphologically cryptic with two other Crepipatella species from Chile, Crepipatella dilatata (Lamarck, 1822) and Crepipatella peruviana (Lamarck, 1822) (a senior synonym of C. fecunda), with respect to adult shell morphology and anatomy. However, Crepipatella occulta is clearly distinguishable from both of them on the basis of embryonic development. It can be distinguished from Crepipatella peruviana, a planktotroph, and Crepipatella dilatata, a direct developer with uncleaved nurse eggs, because it has direct devel-opment with developing nurse embryos that are consumed before the juveniles hatch. Genetic data from DNA sequences also support the distinct status of this species, and show that the South African species C. capensis (Quoy & Gaimard, 1832–33) is more closely related to C. dilatata and C. peruviana than is C. occulta. In addition Crepipatella occulta displays diagnostic alleles in 14 allozyme loci when compared with the other two co-occuring Chilean species in northern Chile. Morphologically, Crepipatella occulta n. sp. does not attain the large size often observed in C. peruviana, and it typically has a shiny dark chest-nut or chocolate shell interior.

**A new species of Callochiton (Mollusca: Polyplacophora) from southern Madagascar**

2023-07-31T15:42:44+12:00

Callochiton cupreus n. sp. is described from Lavanono, southern Madagascar. The new species is compared with the three Callochiton species known from Madagascar, C. vanninii Ferreira, 1983, C. clausadeae Kaas & Van Belle, 1985, and C. levatus Kaas & Van Belle, 1998, and all others known from the Indian Ocean.

**Life history and population dynamics of the surf clam, Mactra veneriformis (Bivalvia: Mactridae), on an estuarine intertidal sandflat in western Kyushu, Japan**

2023-07-31T15:48:20+12:00

Mactra veneriformis occurs commonly on estuarine tidal flats in temperate East Asia. Based on population sampling and recording of environmental variables over an extensive sandflat at a river mouth in Ariake Sound, southern Japan for 39 months, several reproductive traits were monitored and the recruitment, growth, and survivorship for cohorts tracked. The reproductive season ranged from May to September. Each year three to five newly-recruited cohorts appeared in June to October. A single cohort derived from adult spawning in late September occurred in December to January but disappeared by mid-May. Earlier summer recruits reached a maturation size in late September. Each year two or three cohorts survived until next February and fused into a composite cohort. High mortality in juveniles sometimes happened in the rainy period from June to July and at typhoon arrivals in July to October, with increased river discharges. Occasionally juvenile mass mortalities were observed following large wind-induced waves associated with typhoons. Despite their high mortality in the rainy period in some years, the fused adult cohorts contributed solely to the effective reproduction for the entire population. The surviving members of these cohorts died off during the following winter, with an estimated life span of 1.5 years.

Ocean acidification and warming reduce juvenile survival of the fluted giant clam, Tridacna squamosa

2023-07-31T15:58:36+12:00

Anthropogenic carbon dioxide (CO2) emissions are causing ocean acidification and ocean warming; however, the synergistic effects of these stressors on giant clams are completely unknown. Juveniles of the fluted giant clam, Tridacna squamosa Lamarck, 1819, were exposed to present-day control seawater (416 μatm pCO2) and seawater treated with CO2 to simulate ocean conditions predicted for the next 50–100 years (622 μatm pCO2 and 1019 μatm pCO2). These CO2 treatments were cross-factored with seawater temperatures of ~28.5 °C, ~30.0 °C and ~31.5 °C. The majority of mortality occurred between 40 and 60 days. Survival of juveniles decreased with increasing pCO2 and decreased with increasing seawater temperature. The com-bination of the highest pCO2 and both the moderate and highest seawater temperatures resulted in the lowest survival of <20 % indicating survival of T. squamosa could be reduced considerably at ocean conditions predicted to occur around the end of this century.

Index of authors and new taxa in volume 32 (2012)

2023-07-31T16:07:20+12:00

Index with the announcement "Change of publisher for Molluscan Research"